But what happens if you forget the new keyword to create a new Parser? In the middle of a nightly coding session, it might get lost, after all. Worry not, we got you covered! Starting with 0.2.8 you can also leave it out, in which case xml2js will helpfully add it for you, no bad surprises and inexplicable bugs!

Parsing multiple files

If you want to parse multiple files, you have multiple possibilities:

You can create one xml2js.Parser per file. That's the recommended one and is promised to always just work.

You can call reset() on your parser object.

You can hope everything goes well anyway. This behaviour is not guaranteed work always, if ever. Use option #1 if possible. Thanks!

So you wanna some JSON?

Just wrap the result object in a call to JSON.stringify like this JSON.stringify(result). You get a string containing the JSON representation of the parsed object that you can feed to JSON-hungry consumers.

Displaying results

You might wonder why, using console.dir or console.log the output at some level is only [Object]. Don't worry, this is not because xml2js got lazy. That's because Node uses util.inspect to convert the object into strings and that function stops after depth=2 which is a bit low for most XML.

To display the whole deal, you can use console.log(util.inspect(result, false, null)), which displays the whole result.

So much for that, but what if you use eyes for nice colored output and it truncates the output with …? Don't fear, there's also a solution for that, you just need to increase the maxLength limit by creating a custom inspector var inspect = require('eyes').inspector({maxLength: false}) and then you can easily inspect(result).

At the moment, a one to one bi-directional conversion is guaranteed only for default configuration, except for attrkey, charkey and explicitArray options you can redefine to your taste. Writing CDATA is supported via setting the cdata option to true.

Processing attribute, tag names and values

Since 0.4.1 you can optionally provide the parser with attribute name and tag name processors as well as element value processors (Since 0.4.14, you can also optionally provide the parser with attribute value processors):

mergeAttrs (default: false): Merge attributes and child elements as properties of the parent, instead of keying attributes off a child attribute object. This option is ignored if ignoreAttrs is false.

validator (default null): You can specify a callable that validates the resulting structure somehow, however you want. See unit tests for an example.

xmlns (default false): Give each element a field usually called '$ns' (the first character is the same as attrkey) that contains its local name and namespace URI.

explicitChildren (default false): Put child elements to separate property. Doesn't work with mergeAttrs = true. If element has no children then "children" won't be created. Added in 0.2.5.

childkey (default $$): Prefix that is used to access child elements if explicitChildren is set to true. Added in 0.2.5.

preserveChildrenOrder (default false): Modifies the behavior of explicitChildren so that the value of the "children" property becomes an ordered array. When this is true, every node will also get a #name field whose value will correspond to the XML nodeName, so that you may iterate the "children" array and still be able to determine node names. The named (and potentially unordered) properties are also retained in this configuration at the same level as the ordered "children" array. Added in 0.4.9.

charsAsChildren (default false): Determines whether chars should be considered children if explicitChildren is on. Added in 0.2.5.

async (default false): Should the callbacks be async? This might be an incompatible change if your code depends on sync execution of callbacks. Future versions of xml2js might change this default, so the recommendation is to not depend on sync execution anyway. Added in 0.2.6.

strict (default true): Set sax-js to strict or non-strict parsing mode. Defaults to true which is highly recommended, since parsing HTML which is not well-formed XML might yield just about anything. Added in 0.2.7.

attrNameProcessors (default: null): Allows the addition of attribute name processing functions. Accepts an Array of functions with following signature:

function (name){
//do something with `name`
return name
}

Added in 0.4.14

attrValueProcessors (default: null): Allows the addition of attribute value processing functions. Accepts an Array of functions with following signature:

function (name){
//do something with `name`
return name
}

Added in 0.4.1

tagNameProcessors (default: null): Allows the addition of tag name processing functions. Accepts an Array of functions with following signature:

function (name){
//do something with `name`
return name
}

Added in 0.4.1

valueProcessors (default: null): Allows the addition of element value processing functions. Accepts an Array of functions with following signature:

function (name){
//do something with `name`
return name
}

Added in 0.4.6

Options for the Builder class

These options are specified by new Builder({optionName: value}). Possible options are:

rootName (default root or the root key name): root element name to be used in case explicitRoot is false or to override the root element name.

To get the 0.1 defaults in version 0.2 you can just use xml2js.defaults["0.1"] in the same place. This provides you with enough time to migrate to the saner way of parsing in xml2js 0.2. We try to make the migration as simple and gentle as possible, but some breakage cannot be avoided.

So, what exactly did change and why? In 0.2 we changed some defaults to parse the XML in a more universal and sane way. So we disabled normalize and trim so xml2js does not cut out any text content. You can reenable this at will of course. A more important change is that we return the root tag in the resulting JavaScript structure via the explicitRoot setting, so you need to access the first element. This is useful for anybody who wants to know what the root node is and preserves more information. The last major change was to enable explicitArray, so everytime it is possible that one might embed more than one sub-tag into a tag, xml2js >= 0.2 returns an array even if the array just includes one element. This is useful when dealing with APIs that return variable amounts of subtags.

Running tests, development

The development requirements are handled by npm, you just need to install them. We also have a number of unit tests, they can be run using npm test directly from the project root. This runs zap to discover all the tests and execute them.

If you like to contribute, keep in mind that xml2js is written in CoffeeScript, so don't develop on the JavaScript files that are checked into the repository for convenience reasons. Also, please write some unit test to check your behaviour and if it is some user-facing thing, add some documentation to this README, so people will know it exists. Thanks in advance!

Getting support

Please, if you have a problem with the library, first make sure you read this README. If you read this far, thanks, you're good. Then, please make sure your problem really is with xml2js. It is? Okay, then I'll look at it. Send me a mail and we can talk. Please don't open issues, as I don't think that is the proper forum for support problems. Some problems might as well really be bugs in xml2js, if so I'll let you know to open an issue instead :)

But if you know you really found a bug, feel free to open an issue instead.